After few trial of mksquashfs, I think I understood what tiny core was doing. As long as I removed the tcz filename of onboot.lst and reboot, that the original filepath of the tcz would be disappeared from the tcloop. As tcloop wiki said, it is a subdir for all tcz listed in onboot.lst to mount at boot, therefore I could not remove it (it is running). I am from other linux platform, /tmp is a temp place, why tiny core mount tcz there? can I specify my tcz mount other dir? instead the tcloop.
sorry tcpool was a typo.
Thank again for advices.